Polyvinyl alcohol composition



Patented Dec. 31, 1946 I UNITED M TE TENT I 2,413,570 POLYVINYL ALCOHOL COMPOSITION CharlesiJifKrister, Wilmington, Del., and Henry J. Sedusky and George Li'Thompson; Cleveland," hio,-' assignors to E. I. du Pont de Nemours &Company, Wilmington, Del a corpora'tion of Delaware No Drawing. Applicaticin'JunelSI 1943,

Serial N0. 491,394

This invention relates .to compositions comprising polyvinyl alcohol and a clay cooperative therewith and to processes and articles employing such compositions as'adhe'si'v'es, and is" more producing water-resistant joined structures in,

which two or more components are united f'z clein s. (01. 260-32) ant structures so produced.

through a medium of a dried-down e1yvm 1 alcohol-reactive clay film, and by the The processes and compositions of this invenparticularlydirected to adhesive and film -fo'r mtion are applicable in any use where two or more ing compositionscompri'sing polyvinyl alcohol objectsare to be adhesively joined; The compoand .a clay of the type of Chicora'No. 3, to meth- 'sitions are particularly well-suited for use in the ads for producingwater-resistant joined strucjlam'inat'ed board industry, fOr instance, inthe tures comprising aldhesively unitin'g twofo r' more manufacture of corrugated and solid fibreboard. component parts with polyvinyl alcohol reactive The compositionshave physical properties idealclay compositions, and to the water-resistant ly suited'for. use in modern corrugated board or structures so producedf g j solid fibreboard pasting machines, the adhesive It has alread'ybeen proposed to use solutions setting up more rapidly than theadhesives hereof polyvinyl alcohol for v various adhesivepurtof'ore customarily used on such machines; The poses. I-Iovvever,for manypurposes 'polyvinyl'allaminated fibreboard produced is unusually wacohol alone setsmuch' too slowlyto be of any"im ter-resistant, meeting all requirements of waterportant'co'mmercial value; Furthermorajthe ad- "proofness forsuch board. hesive films from a dried-down polyvinyialcohol ,The polyvinyl alcohol usedin a composition of solution are so lacking inj water resistance that this invention suitably may be prepared by hythe suitability of structures jo'inedjwith the poly- -zo"d'roly zing a, polyvinyl acetate solution and hence vinyl alcohol adhesives, is severely restricted for inayj contain some residual polyvinyl acetate. most purposes. variousimeth'o'ds have been pro- Prei'erably, the amount of suchpolyvinyl acetate posed for improving the'waterre'sistance of such should be relatively low. The degree of polymeracihesive films, but most'of thse niethods require iza'tion of'the alcohol should be such as to give athe use of agents which arefrelatively'expensive zs s' y in the solution f fr a ut 2 -to r heat treatments which complicate and ,in- 2200 centipoises measured at a concentration of C ease the cost oi the operation, Also, the addi- '8 to 12%, viscosities in the upper portion of this tion agents heretofore suggested tend to' make 7 "r g being particularly p -I polyvinyl alcohol'adhesive solutions un'stable and p The clay used in a composition of this invento alter their physical propertiesand make them tiqn's'hould be one which'is cooperativ w h e less desirable for use in such operations as the "p lyv nyla l 0 giveawater-insolu P manufacture of laminated fibreboard, where the lot'w a aqu us dispersion of the clay physical properties of the adhesive are critical in l h l i i d wni p i y p the operation of the commercial pasting ma,- ierred to use a clay having" physical and chemical chines used. a f f 5 characteristicssubstantially identical with those It is an object of this invention to provide polyof a clay known as Chicora No. 3,? which'is a vinyl alcohol adhesive co'm'positionsjwhich-set up u h Carolina Cretaceous sedimentary kaolin rapidly after application 'as adhesives ,Another having the following characteristics: object is to provide polyvinyl alcohol adhesives V v which dry down f1 m wa1; r dis ersi at r Chemical analysis Particle size distribution resistant adhesive film s. Anotherobject .is to g a provide water-resistant adhesives based on polyf 1 Per cent Mimi diameter Per cent vinyl alcohol which give water-resistant adhesive l films Without the useof expensive insolubiiizing -3 Above 10 microns; agents. Another objectfi's to provide water-re- 33 12 is sistant structures adhesively joined with adhe- V 0.84 28 sives based on polyvinyl alcohol. Other objects 8:12 3:8 will appear hereinafter. l jv 10.5

The foregoing and related objects of this, in-

Prcsont in combined'forni, calculated as indicated.

7 To make an adhesive of-thisinvention one part by weight of polyvinyl alcohol, on the dry basis,

is mixed with from about A? to 4 parts of clay.

For use in theimanufacture of corrugated board 1 water-resis or laminated fibreboard, it is preferred to use a mixture of about 1 part of polyvinyl alcohol to from 1 to 3 parts of clay, a mixture of 40% polyvinyl alcohol and 60% clay being especially preferred. It is preferred to supply the adhesive to the trade in the form of a dry mixture of alcohol and claysince the cost of transportation of the dry adhesive is materially less, there is no problem of stability of the mixture during storage, and an adhesive solution ma be made up by the user in any concentration adapted to hisparticular needs. It is a unique characteristic of the dry polyvinyl alcohol-clay mixtures of this invention that they are more readily dispersed in water than are the separate components. i

To make an adhesive solution from the dry mixture of polyvinyl alcohol and clay, the mixture is cooked up with water to the desired concentration. This may suitably be done, for instance, by slurrying the solids in cold water and heating the mixture to about 80 C. for /z to 1 hour. The adhesive may then be cooled approximatel to 'room temperature before use.

The concentration of solids in the adhesive solution will depend in any particular instance on the use to which the adhesive is to be applied, but, in general, the solids content preferably may be about from to 25%. For use as a laminating adhesive in making corrugated or solid fibreboard, a solids content of about is preferred and at this concentration it is especially preferred to use a polyvinyl alcohol which with the clay used gives a viscosity in the range of about from 1200 to 2200 centipoises in the liquid adhesive. A polyvinyl alcohol giving a viscosity near the upper end of this range is particularly effective.

The prepared adhesive solution of this invention is a smooth, viscous liquid with considerable tack. It is easy to handle and exhibit a remarkable degree of stability. The material shows no deterioration over considerable periods of time. As used on modern pasting machines the mixture shows a high tack without excessive stringiness or webbing effects. In this respect, the mixture of clay and polyvinyl alcohol is superior to the polyvinyl alcohol alone. i

In using a polyvinyl alcohol-reactive cla water dispersion as an adhesive according to this invention, the a'queousdispersion is applied as a film to one of the surfaces to be united and the second surface is superimposed on the film and heldin place while water is removed. The manner of removing water may be any method adapted to the particular situation. For instance,

in laminated paper-board'water is instantaneously removed by diifusion into the paperboard members which are being joined, followed by evaporation therefrom, the adhesive setting immediately.'

It will be understood that various methods may be used to augment the rate of water removal, such as applying heat or suspending unswelled starch in the polyvinyl alcohol-clay dispersion, the unswelled starch taking up a considerable amount of water upon the application of heat in the paper pasting machine.

Agents designed to promote the setting up of the polyvinyl alcohol-clay mixture may. be applied to the surfaces to be joined. For instance, when using the adhesive in laminated fibreboard. the laminations may be highly sized with rosinalum size or with any other polyvinyl alcoholinsolubilizing agents, of which dimethylol "urea and trimethylol melamine are representative.

In using an aqueous polyvinylalcohol-clay disrsion of this invention for producing laminated fibreboard, the dispersion suitably may be applied at the rate of about from 1 to 6 lbs. per thousand square feet of glue line. Larger amounts may be used under particular circumstances, but ordinarily will not be found necessary or desirable. Smaller amounts, while suitable under special circumstances, are ordinarily in q to give a bond of maximum strength.

The finished adhesivelyjoined structures of this invention are characterized by their remarkable resistance to water. A solid fibreboard made up of laminations joined with a polyvinyl alcohol-clay adhesive of this invention will withstand prolonged soaking in water without showing ply separation. As measured on astandard Mullen testing machine, the wet bursting strength of such board is remarkably higher than with board 7 made using polyvinyl alcohol alone'as the adhevsive.

The invention will be better understood by reference to the following illustrative examples:

Example 1 to 1'70180 F. and maintained at that temperature with stirring for /2 hour; About 40 lbs. of

steam condensed into the mixture to give a final mixture containing 20% solids.

After cooling to room temperature, this adhesive was used directly for the preparation of four-ply solid fibre boxboard on a commercial sealing machine. The paper used was highly alum-rosin sized Kraft, 0.0240.026" thick, 92-424 lbs. per thousand square feet, 64 wide.

Excellent board was made from the start of the machine. There was no separation of the ply and immediate bonding was evident. The machine was operating at a speed of 170-200 feet per minute and the adhesive was applied at the rate of approximately 4-6 lbs. per thousand square feet of glue line.

The prepared board was highly water-resistant. There was no ply separation upon immersion in Water after a period of several months.

Eaiample 2 The following example illustrates the application of an adhesiv of this invention to the production of corrugated board.

A dry mixture of 30% polyvinyl alcohol and 70% Chicora No. 3 clay is used after cooking in water at a solids content of about 25%.

In preparing the liquid adhesive lbs. of dry adhesive is slurried with 370 lbs. of cold water by means of a, mechanical stirrer. When a homogeneous mixture is obtained, live steam is introduced to raise the temperature to I'M-180 F. This temperature is maintained for /2 hour with stirring and the adhesive cooled for use. The live steam will condense suificient water into the mixture to bring the'solids content to approximately evident from the fact that double face board shows no ply separation upon immersion in water after a period of over a month. The adhesive prepares particularly satisfactory board when used with water-resistant. highly alum-rosin sized paper. Under those conditions the corrugated board shows considerable strength at the glue line after immersion in water for several days. I

While in theforegoing description of this in vention certain specific embodiments have been shown, it will be understood that without departing from the scope of the invention those skilled in the art may produce various adhesive compositions and adhesively joined structures and may employ various processes using such adhesives.

We claim: 1. A dry composition adapted to be dispersed in water, comprising one part by weight of polyvinyl alcohol on the dry basis and from V2 to 4 parts of a clay substantially identical with Chicora No. 3.

2. An adhesive and film-forming composition,

' Chicora N0. 3, the mixture having a viscosity,

when dispersed in water to give a 20% solids content, of about from 1200 to 2200 centipoises.

4. A dry composition adapted to be dispersed in water, comprising 40% by weight, on the dry basis, of polyvinyl alcohol and 60% by weight of a clay substantially identical with Chicora No. 3, the mixture having a viscosity, when dispersed in Water to give a 20% solids content, of about from 1200 to 2200 centipoises.

5. An adhesive. and film-forming composition, comprising an aqueous solution of polyvinyl alcohol, the solution containing a clay substantially identical with Chicora No. 3 in an amount 1% times the dry weight of polyvinyl alcohol, the total solids content, dueto polyvinyl alcohol and .,clay, being about 20%, andthe clay-containing solution having a viscosity of about from 1200 to 2200 centipoises.

6. A dry composition adapted'to be dispersed in water, comprising one part by weight, on the dry basis, of polyvinyl alcohol and from /2 to 4 parts of a kaolinite-type clay, the mixture having a viscosity of about from 1200 to 2200 centipoises when dispersed in water to give a 20% solids content.

'7. An adhesive and film-forming composition, comprising an aqueous solution of polyvinyl alcohol containing a kaolinite-type clay, the, clay being present in an amount from V2 to 4 times the weight of the polyvinyl alcohol and the total solids content, due to clay and polyvinyl alcohol,

30 being about from 5 to 25%.

CHARLES J. KRIS'I'ER. HENRY J. SEDUSKY. GEORGE L. THOMPSON. 

